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(CNN)Super Bowl MVP Nick Foles is ecstatic about leading the Philadelphia Eagles to victory, but that's not the triumph he celebrates daily. He gives that medal to his wife, Tori Foles, for what he calls her "amazing strength" in fighting a little-known disorder called postural orthostatic tachycardia syndrome, or POTS.

"They told me I had a virus," said Tori, "but I had never heard of one where you are dizzy all the time. There were a lot of times I couldn't get out of bed."

POTS is a malfunction of the autonomic nervous system, which controls the involuntary functions of the body, such as heart rate, blood pressure, digestion, breathing, blinking and urination. While it can and does affect any part of that system, the most frequent symptoms are profound fatigue, gastrointestinal issues and frequent, almost constant lightheadedness.

Tori and Nick Foles, right, spoke about POTS at a conference this month.

"It was tough for me because I was still healthy," said Nick Foles, "and I could see what she was going through. But she's amazing and we've grown closer together."

The couple spoke Saturday at the annual meeting of Dysautonomia International, a non-profit association dedicated to POTS research, education and patient empowerment.

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"POTS patients do not do well with gravity," said Dr. Satish Raj, medical director of the autonomic investigation unit at the Libin Cardiovascular Institute of Alberta.

"Normally, when you stand up, your heart rate automatically goes up about 10 to 15 beats per minute to increase blood pressure and blood flow and then stabilizes," he explained. "In POTS, it's at least 30 beats a minute within 10 minutes; some can be as high as 60 beats per minute. The brain jumps in to shut that down and you become faint."

"Research from Mayo Clinic shows that the quality of life in POTS patients is similar in what is seen in congestive heart failure, or chronic obstructive pulmonary disease," said Dysautonomia International co-founder and President Lauren Stiles, who is also a POTS patient.

It's estimated POTS affects between 1 and 3 million Americans. But since so few doctors are educated on the symptoms, experts believe numbers could be much higher, both in the US and in the rest of the world. POTS support groups are found in Australia, Brazil, Canada, Egypt, France, Germany, Ireland, Israel, Japan, Mexico, the Netherlands, New Zealand and the United Kingdom.

"How many people are out there? God only knows," said University of Toledo Dr. Blair Grubb, a cardiologist who specializes in autonomic and heart rhythm disorders. "Are there a lot of people out there never diagnosed because they are only moderately impaired?"

"I call it the most common condition you've never heard of," said Stiles, adding that the Mayo Clinic estimates 1 in 100 teens develop POTS.

Not familiar with #POTS? Dysautonomia Awareness Day is coming up on 8/15 at NY's Citi Field. Check it out! #UpgradeYourWorld

The Foles are committed toraising awareness about the disorder. Nick Foles has dedicateda chapter in his new book, "Believe It," to Tori and her struggles with the condition.

"One of the hardest parts was Nick was at the top of his career and our life together was just beginning," said Tori. "But mine was now at rock bottom."

Tori met Nick in college when he was the quarterback for the Arizona Wildcats and she was a setter for the university's volleyball team. The two became good friends and began dating after graduation. When Tori was diagnosed with POTS at age 23, Nick was there to support her. They married in 2014.

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"It's crazy, we spent a whole month at the Mayo Clinic," he told reporters in interviews just days before the Super Bowl. "We got engaged at the Mayo Clinic, we got married at a courthouse two months later because we knew we were in for a run.

"We've never had a wedding ceremony, we've never had a honeymoon, but ... just to see her strength, and to see her determination and her health continue to improve ... it's amazing. It gives me strength because I know she deals with it every single day. I'm grateful that I get to go on this life journey with her."

'Have you looked into depression?'

Eighty percent of POTS sufferers are women and about half, like Tori Foles, are young and relatively healthy when the condition strikes. Because of that, they often struggle to find a doctor who will take their symptoms seriously. In her blog, Tori related her experience with a cardiologist:

"I will never forget when he looked at me in his office and said: 'You are young and healthy. You are in perfect condition. Have you looked into depression or anxiety?' "

She recalled going back later to the same doctor and insisting on further tests.

Diagnostic criteria for POTS

In adults:

A heart rate increase of 30 beats/minute within 10 minutes of standing typically diagnosed with a tilt-table

Absence of orthostatic hypotension

In children:

A heart rate increase of 40 beats/minute within 10 minutes of standing

Absence of orthostatic hypotension

Additional testing may include:

QSART test (measure of autonomic nerves that control sweating)

Thermoregulatory sweat test (measures sweat pattern)

Gastric-emptying tests

Skin biopsy to examine small fiber nerves

Source: Dysautonomia International

"He had me stand up and took my vitals " she wrote. "My heart rate went up by about 40 bpm. BINGO. If your heart rate is increasing by more than 30 bpm upon standing, then you have POTS and your autonomic nervous system is not regulating things. It took 1 minute to figure out. It makes me mad just talking about it."

Despite her struggles, Tori Foles said she was lucky. It only took six weeks before she was diagnosed with POTS. The largest survey on POTS to date, done by Vanderbilt and the University of Calgary, found most people saw an average of seven different doctors over an average of four years before getting a POTS diagnosis. As bad as those statistics sound, it's better today than a decade ago, said Stiles.

"People were getting misdiagnosed for 10 years, 20 years, it was horrible," she said. "And it wasn't just one or two people, it was pretty much everyone."

The survey of 4,178 diagnosed POTS patientsalso found that, like Tori Foles, more than 75% were told their symptoms were psychological; one-fourth said they were treated for a mental disorder before they got an accurate diagnosis. Those numbers were echoed by a study of 779 patients in the UK: 48% were told they had a psychiatric disorder or were hypochondriacs.

Elaine Atha and Valerie Kraft, both 18, are quite familiar with that attitude. "I was told I was anxious and depressed," said Atha. "Several male doctors told me I was just going through puberty."

Kraft said her first cardiologist told her "it was a woman's thing" and was all in her head. "Other doctors told me I was doing it for attention and some anxiety meds would clear it up," she said.

"I was told you're just doing this because you're 31 and don't have babies yet and you are trying to get attention from your husband," recalled Stiles. "That was my personal favorite."

Rough road to diagnosis

"I was bedridden and my GI tract had stopped working. I was getting weird, stabbing pains all over my body," Stiles said.

Stiles was a successful New York lawyer with an active, athletic lifestyle when she suddenly developed POTS symptoms after a snowboarding accident in 2010. POTS patients can often trace the onset of acute symptoms to a specific illness or event, such as a viral illness, major surgery or trauma.

Within four days Stiles was bedridden. She said doctors diagnosed her with everything from "It's all in your head" to a rare neuroendocrine cancer. Doctors even started cancer treatment, but after two months of looking for a tumor "that didn't exist," she said the doctors were baffled and wanted to discharge her.

"So, I put on my lawyer hat and was like, 'I cannot go home bedridden. You are not discharging me until you figure me out. I'm glad it's not cancer, but then what is it?' " Stiles remembered asking a doctor. "And the doctor literally shrugged his shoulders and walked out of my hospital room."

Frustrated and frightened, Stiles went onto the internet and began googling her symptoms. She found what appeared to be the answer: POTS. She printed 30 journal articles, highlighted her symptoms and wrote her test results in the margins where they matched a description. Then she handed the papers to her neurologist and asked him to read.

"Of course, the neurologist said to me, 'Don't go on the internet,' " said Stiles. "But he took them home. He read it overnight. And he came back the next morning and I kid you not, he said'Holy s***! You have POTS.' "

Members of Dysautonomia International lobbying for funding for POTS research.

An annual meeting drew growing numbers of patients and their loved ones eager for information and support. Stiles began inviting major research institutions to the conferences, and excited by the chance to examine hundreds of people diagnosed with POTS in one location, they began collecting family history, medical test results, and blood serum samples from attendees.

Research into POTS is critical, say experts, because so little is known about why the autonomic nervous system malfunctions. Symptoms vary from person to person, and may be triggered by a wide variety of underlying diseases and conditions.

Researchers are investigating a possible connection between POTS and autoimmune markers, genetic markers, hormones such as norepinephrine, and mast cell activation -- a sort of allergic response. Other scientists are looking deeper into the devastating symptoms of POTS, includingcognitive dysfunction, gastric distress, fainting and poor sleep.

At this time, treatment for POTS is limited. Some medications, used off label, can help in the short term; long-term efficacy is not known. Most POTS patients are told to treat their symptoms with lifestyle adjustments, including drinking two to three liters of fluids a day, wearing compression stockings to improve blood flow and doing an hour a day of reclined exercise, such as swimming, rowing or recumbent biking.

"When you're in the acutely ill bedridden or nearly bedridden state, exercise can seem impossible," Stiles said. "But you just have to do the right kind of exercise, at the right pace and build up a tolerance." Dysautonomia International has suggested exercises for each level on its website.

Considering society's push to limit salt due to the explosion of hypertension, the most unusual recommendation given to POTS patients is to add up to 10,000 milligrams of salta day to their diet.

"They should pickle themselves," said Raj. "Add V8 tomato juice, soy sauce, lots of salty foods, or take salt supplements along with the three liters of water. You want to increase blood volume and flow to the heart."

While the condition can be devastating -- the POTS survey found 33% of respondents had applied for disability benefits -- most people can lead somewhat normal lives. A Mayo Clinic survey asked pediatric POTS patients seen between 2003 and 2010 about their long-term prognosis. Nineteen percent of respondents said they had fully recovered; 51% had persistent but improved POTS symptoms; and 16% had intermittent issues.

"It's variable," said Stiles. "There are some patients who have it who are flat-out bed ridden and can't even get to the doctor. And then there are other people who have it who literally can climb mountains."

Nick and Tori Foles celebrate with baby Lily at the Super Bowl.

For Nick and Tori Foles, their "mountain" was adding a baby to their family.Daughter Lily James was born in June 2017.

"I always knew I wanted to have children, but there were days I couldn't take care of myself," said Tori, "so how could I take care of a baby?"

But as she focused on eating healthy, meditating, getting plenty of sleep, drinking fluids and exercising, she found she was able to rise to the challenge.

"I've had to be more disciplined in order to take care of her," said Tori. "Having a system and routine is important."

"We've gone through this journey and it's put everything into perspective," added Nick."We're keeping out priorities straight, our faith, our family, then whatever comes after that. Football is down the list because we have our priorities straight."

Editor's note: The author of the story has a family member recently diagnosed with POTS.